OFFSET
1,9
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..262
FORMULA
u(4 - n) = u(n) for all n in Z.
0 = u(n) * u(n+3) - u(n+1) - u(n+2) for all n in Z. - Michael Somos, Nov 01 2014
EXAMPLE
u(1), ... = 1, 1, 1, 2, 3, 5, 4, 3, 7/5, 11/10, 5/6, 29/21, 155/77, 224/55, 639/145, ...
MATHEMATICA
Denominator[RecurrenceTable[{u[1] == u[2] == u[3] == 1, u[n] == (u[n - 1] + u[n - 2])/u[n - 3]}, u, {n, 50}]] (* G. C. Greubel, Jun 27 2017 *)
PROG
(PARI) {u(n) = local(v = [1, 1, 1]); if( n<1, n = 4-n); if( n<4, 1, for( k=4, n, v = [v[2], v[3], (v[2] + v[3]) / v[1]]); denominator( v[3] ))};
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Michael Somos, Jan 27 2012
STATUS
approved